CVE-2026-33753

MEDIUMNVD 6.26.2—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 6.2 under NVD CVSS v3. EPSS exploit probability: 0.0%, top 99% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
Elevated
6.2
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS: 0%CVSS: 6.2Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

rfc3161-client is a Python library implementing the Time-Stamp Protocol (TSP) described in RFC 3161. Prior to 1.0.6, an Authorization Bypass vulnerability in rfc3161-client's signature verification allows any attacker to impersonate a trusted TimeStamping Authority (TSA). By exploiting a logic flaw in how the library extracts the leaf certificate from an unordered PKCS#7 bag of certificates, an attacker can append a spoofed certificate matching the target common_name and Extended Key Usage (EKU) requirements. This tricks the library into verifying these authorization rules against the forged certificate while validating the cryptographic signature against an actual trusted TSA (such as FreeTSA), thereby bypassing the intended TSA authorization pinning entirely. This vulnerability is fixed in 1.0.6.

CVSS v3
6.2
EG Score
6.2(medium)
EPSS
8.5%
KEV
Not listed

Published

April 8, 2026

Last Modified

April 21, 2026

Advisory Details (1)

Auto-updated Jun 15, 2026
🔬 Proof of concept available. Patch available. Sources: github.
github Patch Available🟡 PoC Available

Improper Certificate Validation in rfc3161-client · Advisory · trailofbits/rfc3161-client · GitHub

https://github.com/trailofbits/rfc3161-client/security/advisories/GHSA-3xxc-pwj6-jgrj

Affected Packages

(1 across 1 ecosystem)
PyPI(1)
PackageVulnerable rangeFixed inDependents
rfc3161-client0.0.2 ... 1.0.5 (12 versions)1.0.6—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 9× in last 7d / 42× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-07-12 05:46 UTCEPSS rescore
  2. 2026-07-11 08:27 UTCEPSS rescore
  3. 2026-07-09 19:10 UTCEPSS rescore
  4. 2026-07-08 15:15 UTCEPSS rescore
  5. 2026-07-07 13:46 UTCEPSS rescore
  6. 2026-07-06 16:27 UTCEPSS rescore
  7. 2026-07-06 16:27 UTCEPSS rescore
  8. 2026-07-06 02:23 UTCEPSS rescore
  9. 2026-07-06 02:23 UTCEPSS rescore
  10. 2026-07-05 02:30 UTCEPSS rescore
  11. 2026-07-04 06:31 UTCEPSS rescore
  12. 2026-07-01 15:06 UTCEPSS rescore
  13. 2026-06-30 23:22 UTCEPSS rescore
  14. 2026-06-29 14:06 UTCEPSS rescore
  15. 2026-06-29 14:06 UTCEPSS rescore
  16. 2026-06-28 14:07 UTCEPSS rescore
  17. 2026-06-28 14:07 UTCEPSS rescore
  18. 2026-06-28 04:56 UTCEPSS rescore
  19. 2026-06-28 04:56 UTCEPSS rescore
  20. 2026-06-27 03:08 UTCEPSS rescore
  21. 2026-06-25 13:49 UTCEPSS rescore
  22. 2026-06-25 13:49 UTCEPSS rescore
  23. 2026-06-24 14:05 UTCEPSS rescore
  24. 2026-06-23 21:33 UTCEPSS rescore
  25. 2026-06-23 21:33 UTCEPSS rescore
Show 60 more
  1. 2026-06-22 14:25 UTCEPSS rescore
  2. 2026-06-22 14:25 UTCEPSS rescore
  3. 2026-06-21 14:56 UTCEPSS rescore
  4. 2026-06-21 14:56 UTCEPSS rescore
  5. 2026-06-21 01:59 UTCEPSS rescore
  6. 2026-06-19 19:25 UTCEPSS rescore
  7. 2026-06-19 19:25 UTCEPSS rescore
  8. 2026-06-18 17:52 UTCEPSS rescore
  9. 2026-06-18 17:52 UTCEPSS rescore
  10. 2026-06-17 17:53 UTCEPSS rescore
  11. 2026-06-16 17:52 UTCEPSS rescore
  12. 2026-06-15 17:49 UTCEPSS rescore
  13. 2026-06-15 05:46 UTCEG score recompute
  14. 2026-06-14 23:18 UTCEPSS rescore
  15. 2026-06-13 23:00 UTCEPSS rescore
  16. 2026-06-12 23:12 UTCEPSS rescore
  17. 2026-06-12 23:12 UTCEPSS rescore
  18. 2026-06-11 20:58 UTCEG score recompute
  19. 2026-06-11 14:00 UTCEPSS rescore
  20. 2026-06-10 22:18 UTCEPSS rescore
  21. 2026-06-10 13:22 UTCEPSS rescore
  22. 2026-06-10 13:22 UTCEG score recompute
  23. 2026-06-09 13:21 UTCEG score recompute
  24. 2026-06-08 14:17 UTCEPSS rescore
  25. 2026-06-08 14:17 UTCEPSS rescore
  26. 2026-06-08 09:08 UTCEG score recompute
  27. 2026-06-07 15:25 UTCEPSS rescore
  28. 2026-06-07 15:25 UTCEPSS rescore
  29. 2026-06-07 15:25 UTCEPSS rescore
  30. 2026-06-07 09:09 UTCEG score recompute
  31. 2026-06-06 13:47 UTCEPSS rescore
  32. 2026-06-06 13:47 UTCEPSS rescore
  33. 2026-06-05 22:47 UTCEPSS rescore
  34. 2026-06-05 22:47 UTCEPSS rescore
  35. 2026-06-04 13:12 UTCEPSS rescore
  36. 2026-06-04 13:12 UTCEPSS rescore
  37. 2026-06-02 20:13 UTCEPSS rescore
  38. 2026-06-01 13:52 UTCEPSS rescore
  39. 2026-06-01 13:52 UTCEPSS rescore
  40. 2026-06-01 13:51 UTCEPSS rescore
  41. 2026-05-31 00:16 UTCEPSS rescore
  42. 2026-05-31 00:16 UTCEPSS rescore
  43. 2026-05-31 00:16 UTCEPSS rescore
  44. 2026-05-29 13:44 UTCEPSS rescore
  45. 2026-05-29 13:44 UTCEPSS rescore
  46. 2026-05-28 13:44 UTCEPSS rescore
  47. 2026-05-28 13:44 UTCEPSS rescore
  48. 2026-05-28 13:44 UTCEPSS rescore
  49. 2026-05-27 13:40 UTCEPSS rescore
  50. 2026-05-27 13:40 UTCEPSS rescore
  51. 2026-05-27 13:40 UTCEPSS rescore
  52. 2026-05-26 13:44 UTCEPSS rescore
  53. 2026-05-26 07:18 UTCEPSS rescore
  54. 2026-05-26 07:18 UTCEPSS rescore
  55. 2026-05-23 00:08 UTCEG score recompute
  56. 2026-05-20 22:38 UTCEPSS rescore
  57. 2026-05-20 22:38 UTCEPSS rescore
  58. 2026-05-20 18:21 UTCEG score recompute
  59. 2026-05-20 11:22 UTCEPSS rescore
  60. 2026-05-20 11:22 UTCEPSS rescore

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-33753?
CVE-2026-33753 is a medium vulnerability published on April 8, 2026. rfc3161-client is a Python library implementing the Time-Stamp Protocol (TSP) described in RFC 3161. Prior to 1.0.6, an Authorization Bypass vulnerability in rfc3161-client's signature verification allows any attacker to impersonate a trusted TimeStamping Authority (TSA). By exploiting a logic flaw…
When was CVE-2026-33753 disclosed?
CVE-2026-33753 was first published in the National Vulnerability Database on April 8, 2026, with the most recent update on April 21, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-33753 actively exploited?
CVE-2026-33753 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 8.5% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-33753?
CVE-2026-33753 has a CVSS v3 base score of 6.2 (NVD).
How do I remediate CVE-2026-33753?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-33753, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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